The structure of organic electroluminescent devices (OLEDs) in which organic semiconductors are employed as functional materials is described, for example, in U.S. Pat. Nos. 4,539,507, 5,151,629, EP 0676461 and WO 98/27136. The emitting materials employed are frequently organometallic complexes which exhibit phosphorescence instead of fluorescence. For quantum-mechanical reasons, an up to four-fold increase in energy and power efficiency is possible using organometallic compounds as phosphorescence emitters. In general, there is still a need for improvement, for example with respect to efficiency, operating voltage and lifetime, in the case of OLEDs, in particular also in the case of OLEDs which exhibit triplet emission (phosphorescence). The properties of phosphorescent OLEDs are not determined only by the triplet emitters employed. In particular, the other materials used, such as, for example, matrix materials, are also of particular importance here. Improvements in these materials may thus also result in significant improvements in the OLED properties.
In accordance with the prior art, inter alia carbazole derivatives (for example in accordance with WO 2014/015931), indolocarbazole derivatives (for example in accordance with WO 2007/063754 or WO 2008/056746) or indenocarbazole derivatives (for example in accordance with WO 2010/136109 or WO 2011/000455), in particular those which are substituted by electron-deficient heteroaromatic compounds, such as triazine, are used as matrix materials for phosphorescent emitters. WO 2011/046182 discloses carbazole-arylene-triazine derivatives which are substituted on the triazine by a fluorenyl group. WO 2013/077352 discloses triazine derivatives in which the triazine group is bonded to a dibenzofuran group via a divalent arylene group. These compounds are described as hole-blocking materials. Use of these materials as host for phosphorescent emitters is not disclosed. KR 2014-0046541 discloses carbazole-triazine-dibenzofuran and carbazole-triazine-dibenzothiophene compounds in which the dibenzofuran or dibenzothiophene is bonded to the triazine via its 4-position.
In general, there is still a need for improvement in the case of materials for use as matrix materials, in particular with respect to the lifetime, but also with respect to the efficiency and the operating voltage of the device.